In the recent fine processing technique represented by the LSI manufacturing technique, according to miniaturization of a pattern, improvement in the yield is getting difficult. Therefore, the pattern measurement and the shape inspection performed after the lithography and the etching becomes more important than ever in the following two points. The first point is a pass or fail judgment by an observer himself or herself. During the manufacturing processes, finding a defect in as early stage as possible to retry the processing or abandon the above defect improves the productivity in the end. The second point is a monitoring of the state of a processing device and the process. When a trouble of a device and an error on the process are detected through an inspection, the result is fed back, hence to make it possible to avoid a further failure in the processing. The basic pattern used in the manufacturing process is a line pattern and therefore, the size of a fine line pattern and the shape inspection at high accuracy are important for improving the productivity of a product.
The size of a target pattern is miniaturized in 100 nm and less; therefore, the above mentioned inspection is performed by electron microscopic observation in many cases. The effective inspection method of a fine pattern is to analyze the observation image above the pattern, which is obtained with a Scanning Electron Microscope (SEM). When the size of the pattern is some hundreds nm or more, it may be similarly observed and analyzed from the above with a laser microscope. In any case of using the SEM and the laser microscope, only the observation cannot detect the pattern accurately and cannot be applied to the production management. It is necessary to calculate an indicator enabling a pass or fail judgment on the pattern through analysis on the observation image from the above. So far, the size of an important pattern, of the device patterns, from a viewpoint of the product performance management is called Critical Dimension, or CD, which has been regarded as an indicator. According to the miniaturization of the pattern, however, not only an average CD but a local fluctuation (Linewidth roughness, or LWR) of line width caused by the microscopic asperities in a line pattern edge (Line-edge roughness, or LER) have to be quantified for the use as an indicator. Even when the CD is as designed, if the LWR is larger, the performance of a device is insufficient. This is specifically described in Non-Patent Literature 1.
When further miniaturization proceeds, when the pitch of the line pattern becomes 80 nm or less, a new phenomenon occurs. This is such a phenomenon that, with the width of a line kept at constant, the position of the center of the line is fluctuated. When there is a deterioration of the line shape (hereinafter, called wiggling), for example, the resistivity of LSI wiring is deviated from the design value, and a short or an open failure occurs when the overlapping error between the upper and lower layers becomes large. Therefore, this has to be detected. Here, when wiggling occurs after the formation of a pattern and when a line is formed with the line center position fluctuated from the start, it is similarly called wiggling in the both cases.
This wiggling, however, cannot be detected by the conventional CD measurement and the LWR measurement. This is because the CD and the LWR do not change regardless of the presence of the wiggling. The LER measurement can detect the wiggling; however, even in this case, it cannot be distinguished from the ordinal LER in which the left and right of a line are not synchronized, naturally generated at random by the unevenness of a resist material and in the development process. This phenomenon is taken, for example, in the above Non-Patent Literature 1. In this document, since wiggling is found when the size value of a line pattern is a predetermined value or less, the maximum pattern size that may have the wiggling is set at an indicator, under the condition of pattern forming process and according as the size value is smaller, the process is evaluated better.
As a trial of quantifying the degree of wiggling in a line pattern, there is proposed an evaluating method by an indicator in combination of LER, LWR, and SWR (Space width roughness) in Non-Patent Literature 2.
Other than the above, for the purpose of seeking for a cause of the LER, there is proposed a method of correlating the shape between left and right edges of a line. This is disclosed in Patent Literature 1.